I've never used valet parking at any cruise terminal but it all comes down to cost vs. convenience. If the convenience is worth it for you then, by all means, do it.
I almost always use on site parking at airports. I pay about $4 more per day but it is worth it to just walk out of the terminal and onto the ramp and to my car. I hate waiting for the shuttle and being drove two miles away and then finding my car.